1. Field of the Invention
The present invention relates generally to detecting an unseated condition of a component and, more particularly, to a RFID linking device-based switchable sensor, a component having the switchable sensor, and a switchable sensor system for detecting a component with the switchable sensor in an unseated condition with respect to another component.
2. Description of the Related Art
A conventional inkjet printing system forms an image on a print medium by ejecting ink from a plurality of ink jetting nozzles of an inkjet printhead to form a pattern of ink dots on the print medium. Inkjet printing is accomplished without contact between the printing system and the print medium. Such printing system also typically includes one or more items that may be replaced once fully consumed during the printing operation. One such consumable item is a semi-permanent inkjet printhead itself and another is a replaceable ink container or tank in which ink is stored. In one embodiment of such inkjet printing system, the semi-permanent printhead is mounted by a reciprocating carrier where at least one replaceable tank when seated within the carrier is engaged in a sealed ink supplying or delivery relationship with the printhead. Once seated, the carrier transports the semi-permanent printhead and the replaceable tank across the print medium along a bi-directional scanning path defining a print zone of the printer. A sheet feeding mechanism is used to incrementally advance a sheet of the print medium in a feed direction, also commonly referred to as a sub-scan direction, through the print zone between scans in the main scan direction, or after all data intended to be printed on the print medium at a particular stationary position has been completed.
Thus, an inkjet printing system including a semi-permanent printhead and a replaceable ink tank is well known. One such inkjet printing system is marketed by Lexmark International, Inc. wherein the at least one ink tank used by the system when fully installed and seated within the reciprocating carrier interfits, in a seated ink delivery relationship, with the semi-permanent printhead mounted by the carrier below the ink tank. An overriding constraint in the design of this inkjet printing system is that costs be kept to a minimum. Only the minimum mechanical physical connections, and ink storage and plumbing requirements are provided. Any added electronics or similar devices are generally not desirable due to their added costs.
In this prior art Lexmark inkjet printing system, then, at least one replaceable ink tank is utilized and also a carrier is utilized for receiving and seating the ink tank. The carrier has a latch or retaining clip which releasably snap fits with the ink tank when the tank is seated within the carrier and interfitted with the printhead. However, one undesirable tradeoff in achieving the overriding cost constraint in the design of this inkjet printing system has been that there is no means provided for automatic detecting that the ink tank is not fully inserted and seated within the carrier so as to be properly engaged and interfitted with the semi-permanent printhead. FIGS. 2-4 show prior art sequences of successive positions of a tank relative to a carrier and printhead, ranging from the tank in an unseated position in FIG. 2, to next the tank almost in the seated position in FIG. 3, to finally the tank in the seated position in the carrier in FIG. 4. If it is not fully intermitted in the sealed ink delivery relationship with the semi-permanent printhead as seen in FIG. 4, the tank will not operate properly and may leak, causing machine damage. Also, depending on the carrier design and machine cover design around the carrier and tank loading area, damage might result from the tank hitting the machine covers.
Previous approaches to detecting presence/absence, misplacement, or seating of a tank or cartridge in the carrier are known in the prior art. Representative of the prior art are the following patents.
U.S. Pat. No. 5,997,121 to Altfather et al. discloses a low ink sensing system combined with a cartridge detection system which together employ a prism, a mirror, light sources and a photosensor coating such that when a carriage is positioned at a sensing station if a reflected beam is not detected then the cartridge is not present in the carriage.
U.S. Pat. No. 6,467,869 to Merz et al. discloses cartridges with exterior marks arranged to form a pattern that is electronically scanned by a printer to identify and verify that an appropriate cartridge combination has been installed.
U.S. Pat. No. 6,739,689 to Choi discloses an apparatus operable to identify the type of cartridge mounted in a carriage or if any cartridge is present. The apparatus has identifying units, such as protrusions, reflective surfaces or flexible printed circuits with electrical contact node structures, provided on the cartridge body, a sensing unit on the carriage to sense the identifying unit, and a micro processing unit to make the identification by using signals from the sensing unit. The sensing unit includes light sensors in the form of light emitters and detectors or micro switches operated by the protrusions.
U.S. Pat. No. 6,805,430 to Chen et al. discloses an apparatus having a carriage receiving a cartridge, a sensor to detect color of identifiable areas on the cartridge being associated with color of ink in the cartridge, and a control unit to receive a signal from the sensor to determine whether the cartridge is correctly placed in the carriage; if misplaced, a warning signal is generated to alert the user. The sensors and identifiable areas are charge coupled devices or contact image sensors capable of electrically coupling with one another; alternatively, signals between sensors and control unit can be transmitted and received by wireless methods, such as infrared data association, RF transmission or radio transmission.
U.S. Pat. No. 7,125,109 to Watanabe et al. discloses electrical contacts on an ink container and container holder which make electrical connections with one another when the ink container is seated in the container holder.
U.S. Pat. No. 7,157,727 to Kimura discloses an optical detector able to sense presence of a cartridge by using a signal from light sending and receiving parts on the carriage adjacent to the bottom of the cartridge wherein the light can be both refracted and reflected to determine whether the cartridge is present and to determine how much ink is left.
A common drawback of these approaches is that they all require the addition of electrical and/or optical parts that come at a significant and unacceptable increase in cost.
Another approach previously suggested to sense an unseated ink tank without the addition of costly parts is to move the carrier slowly away from the loading position after the cover is closed (after a tank loading or change). Then, if a tank is not fully inserted and seated, this approach assumes it will stall the carrier when the unseated tank interferes with the covers. However, while this approach can be implemented at no increased hardware cost, the assumption that an unseated tank will hit the covers may not be valid. An upper end of an unseated tank, as seen in FIGS. 2 and 3, is not necessarily high enough to interfere with the covers. Also, even if a carrier stall does occur, this approach would provide a system in which a true carrier stall occurring after a tank install is indistinguishable from an improperly installed tank.
Also, it is taught in U.S. Pat. Application Publication No. 2007/0040876 to Anderson et al. whose invention is assigned to the same assignee as the present invention, to use a RFID linking device, such as a RFID tag, on components that are consumable and replaceable, such as ink cartridges or tanks. The RFID tags are employed for purposes of identification to the printer of ink usage, part number, serial number, etc. of the replaceable components. The added cost of usage of these devices is thought to be justified to ensure compatibility between replaceable components and printers so as to maintain high print quality and reliable operation. However, there is no recognition that a RFID linking device might be useful per se in detecting an unseated consumable cartridge or tank or enabled for such use through making a modification to the RFID linking device.
Thus, there is still a need for an innovation that will automatically detect the aforementioned unseated tank condition with minimal added cost to the design of the inkjet printing system.